Amphibians have smooth moist skin. The toad
is an exception with rough dry skin.

The majority of amphibians contain four
limbs with no claws on their digits (toes).

They contain a three chambered heart. Two
atria and one ventricle. There is a possibility of the
oxygenated and unoxygenated blood mixing in the
ventricle.

They are ectotherms. During extreme
environmental conditions they either
hibernate (winter) or
aestivate (summer).

They carry on external fertilization. Their
offspring develop through a process called
metamorphosis. Tadpoles (aquatic
larvae) resemble fish. Over a period of time they change in
form into the adult amphibian.

They respire through poorly developed lungs
and moist skin.

They contain a well developed muscular
system.

The digestive system is adapted to digest
whole prey, swallowed by the organism.

Two kidney's rid the body of nitrogenous
waste. The amphibian liver carries on several functions:
detoxifying poisons, producing bile, and storing glucose in the
form of glycogen.

The cloaca is
a sac that collects discharge from the large intestine, urinary
bladder, and gonads before it is eliminated from the
body.

Their brain is well developed and is
attached to a dorsal nerve cord.

Most amphibians contain three eye lids. Two
are normal and one is transparent.

These are the first animals to possess a
pressure releasing canal called the Eustachian
tube. The tube connects the mouth cavity
with the tympanic
membrane.

Order Apoda. This order contains
amphibians without legs. Examples of this order are the
caecilians. Most of these organisms live in the moist soil,
while some tropical species live in ponds and
streams.

Order Urodela. These are tailed
amphibians. Included in this group are the salamanders and
newts. These animals contain a tail and neck. Some of these
organisms never develop lungs and must rely on external
gills.

Order Anura. Frogs and toads
represent these tailless organisms. Frogs use powerful hind
legs for movement. Their long sticky tongue is attached to the
tip of the lower jaw. They exhibit a variety of colorful skin,
which is sometimes poisonous. Frogs live in many areas of the
world. The male is the only one of the species that makes
sounds.